1. Field of the Invention
The present invention relates to a driving control apparatus for an engine of a vehicle in which a mutual communication is conducted between a first control unit for calculating an engine parameter and a second control unit for driving a throttle and a redundant sensor is used with respect to a throttle opening degree and an accelerator opening degree, and more particularly, to a driving control apparatus for an engine of a vehicle which is capable of judging an abnormality of the second control unit when the communication between the control units is abnormal.
2. Description of the Related Art
There is a conventionally known driving control apparatus for an engine of a vehicle comprising a first control unit for calculating control parameters with respect to the engine in accordance with its driving state including the accelerator opening degree and the throttle opening degree, a second control unit for calculating a control amount of a throttle actuator in accordance with a target throttle opening degree included in the control parameters, and redundant sensors corresponding to the respective control units.
FIG. 9 is a block diagram showing such a conventional driving control apparatus for the engine of the vehicle as described in Japanese Patent Application Laid-open No. 5-202793 for example.
In FIG. 9, an engine 1 mounted in the vehicle comprises a cylinder and a piston connected to a crankshaft (not shown), and also comprises an intake pipe 2 and an exhaust pipe 3 which are in communication with a combustion chamber in the cylinder, and a spark plug 4 disposed in the combustion chamber.
Provided in the intake pipe 2 are an injector 5 for injecting a fuel, and a throttle valve 6 for adjusting an air amount to be drawn into the engine 1.
Provided in the throttle valve 6 are a throttle actuator 7 including a motor for driving the throttle valve 6, and a throttle position sensor (which will be referred to as TPS hereinafter) 8 for detecting a position of the throttle valve 6 as a throttle opening degree.
The TPS 8 includes first and second throttle position sensor portions (which will be referred to as first and second TPS portions hereinafter) 8a and 8b for outputting first and second throttle opening degree signals T1 and T2 which are mutually redundant.
An accelerator pedal 9 which is to be depressed by a driver is provided with an accelerator pedal position sensor (which will be referred to as APS hereinafter) 10 for detecting a position of the accelerator pedal 9 as an accelerator opening degree.
The accelerator pedal position sensor 10 includes first and second accelerator pedal position sensor portions (which will be referred to as first and second APS portions hereinafter) 10a and 10b for outputting first and second accelerator opening degree signals A1 and A2 which are mutually redundant.
Not only the illustrated TPS 8 and APS 10, but also known drawn air amount sensor, crank angle sensor, water temperature sensor and the like are of course included as various sensors for detecting the driving states of the engine 1, although they are not illustrated for simplification.
A first control unit 11 comprising a microcomputer calculates a control parameter with respect to the engine 1 in accordance with driving states (various sensed information) including the accelerator opening degree and the throttle opening degree.
Although a spark signal P with respect to the spark plug 4 and an injection signal J with respect to the injector 5 are indicated here as typical control parameters, other parameters such as a target throttle opening degree with respect to the throttle valve 6 are also calculated.
A second control unit 12 comprising a microcomputer calculates a control amount with respect to the throttle actuator 7 in accordance with the target throttle opening degree calculated in the first control unit 11, and outputs the result as a motor driving signal M.
A first communication line L1 for transmitting data from the first control unit 11 to the second control unit 12, and a second communication line L2 for transmitting data from the second control unit 12 to the first control unit 11 are provided between the first and the second control unit 11 and 12 as buses for conducting a mutual communication.
In this case, the first accelerator opening degree signal A1 and the first throttle opening degree signal T1 are input to the first control unit, and are input to the second control unit 12 through the first communication line L1.
Further, the second accelerator opening degree signal A2 and the second throttle opening degree signal T2 are input to the second control unit 12, and are input to the first control unit 11 through the second communication line L2.
Each of the control units 11 and 12 compares the accelerator 7 opening degree signals A1 and A2, and judges whether or not there exists abnormality of the APS 10 based on the comparison results (agree or disagree) made by the control units 11 and 12.
Similarly, each of the control units 11 and 12 compares the throttle opening degree signals T1 and T2, and judges whether or not there exists abnormality of the TPS 8 based on the comparison results (agree or disagree) made by the control units 11 and 12.
The conventional apparatus constructed as described above judges whether or not there exists an abnormality of the redundant sensors (TPS 8 and APS 10) connected to the control units 11 and 12, and when the apparatus judges that there exists any abnormality, the apparatus carries out appropriate management, e.g., by reducing the target throttle opening degree to suppress the engine output, or by replacing a sensor which is determined as being abnormal.
However, the conventional apparatus does not judge an abnormality in operation of the second control unit 12 for driving the throttle, and no attention is paid as to what management should be carried out when the second control unit 12 is determined as being abnormal.
Therefore, even when sensors are in normal condition, if the throttle valve 6 is fully opened due to an abnormality of the second control unit 12, there is fear that the vehicle may run recklessly.
As described above, although the conventional driving control apparatus for an engine of a vehicle judges an abnormality of the TPS 8 and APS 10 connected to the control units 11 and 12, the apparatus does not judge an abnormality of operation of the second control unit 12. Therefore, there is a problem that a running performance of the vehicle may be deteriorated due to an abnormality in operation at the side of the second control unit 12, even if sensors are in normal condition.